The present invention relates to a device for taking waste samples and, in particular, to such a device suitable for taking samples of hazardous waste fluid, such as toxic or radioactive fluid, from a drum or tank.
In the field of hazardous waste it is frequently necessary to determine the chemical composition of waste fluid contained in a drum or tank. Because of the stratification that often occurs in such fluids over time, it is necessary to sample each successive layer from the top to the bottom of the containing drum in order to obtain a sample accurately representative of the waste fluid contained therein. Accurate measurement of hazardous waste content is important, both to workers in the field and to the public, to prevent inappropriate handling, storage, or disposal that could endanger health. An additional concern affecting both measurement accuracy and safety is the adherence of amounts of hazardous material to the surfaces of the sampling device itself, leading to increased risk of harmful exposure to operators of the device during the sampling procedure, and to subsequent measurement errors due to cross contamination between the chemicals in separate drums.
One prior device designed for the sampling of hazardous fluid, developed by the Environmental Protection Agency and the State of California, is the Coliwasa or composite liquid waste sampler. Typically, the Coliwasa sampler comprises a hollow tube in which is disposed a rigid rod for controlling a valve in a fluid inlet at the bottom of the tube. After the hollow tube has been slowly lowered into the waste fluid with the inlet open, thereby permitting successive layers of waste fluid to collect inside the tube, the rigid rod is manipulated so that the inlet opening of the hollow tube is closed by the valve, whereupon the tube may be lifted out of the drum with the representative fluid column intact. The worker then repositions the tube over a collection vessel and opens the valve to discharge the fluid. The tube and rod of the sampler are both constructed of glass prescored to enable subsequent breakage and permanent disposal in the drum, thereby avoiding subsequent cross-contamination or the hazards of cleanup. However, during the sampling procedure there is a high likelihood of exposure to hazardous material because the operator is required to lift from the drum a long tube that is coated with hazardous material and from which hazardous material may drip and splash.
Another device suitable for sampling hazardous fluid from a tank is the VACSAM.TM. or vacuum-operated composite liquid sampler. This device is made by Geotech Environmental Equipment Incorporated of Denver, Colo. Like the Coliwasa, the VACSAM.TM. employs a hollow sampling tube, but relies on a vacuum pump to draw the fluid out of the top of the tube through flexible tubing into a collection bottle. Because the immersed portion of the tube remains in the drum during sampling, exposure of the operator to hazardous material is minimized. Furthermore, if the tube is constructed of scored glass, the tube may be broken while still immersed in the drum thereby permitting disposal of the tube, along with the flexible tubing, in the original drum being sampled. In the VACSAM.TM. device, however, the fluid from the bottom layers of a stratified fluid in the drum mixes with the representative sample through the bottom of the tube as the pump draws the representative sample upward, making the device susceptible to inaccuracies in sampling.
Additional sampling devices are disclosed in Renfro, U.S. Pat. No. 2,158,803 and Crumal, U.S. Pat. No. 3,813,945. While their features are of interest, these devices are not suitable for sampling hazardous fluids because their construction makes them difficult to decontaminate and because they are too expensive for disposal after a single sampling. In any case, the structures of these devices could not be disassembled for disposal without removing them from the fluid being sampled, thereby exposing their operators to the fluid.
What is required, then, is a hazardous waste sampler that both accurately collects a representative sample of a stratified fluid, and thereafter enables immediate disposal of the sampler in the drum from which the sample has been taken, all without ever requiring the removal of the immersed portion of the sampler from the drum, so as to avoid exposing the operator to the hazardous material sampled.